To collect blood, currently, blood component collection is adopted for the purposes of effectively utilizing blood and alleviating a burden a donor must incur. Namely, the collected blood is separated into components through centrifugation or the like, only a component needed for a patient to be transfused is collected, and the other components are restored to a donor.
In the component collection, for preparing a platelet product, blood collected from a donor is routed to a blood component collection circuit. A centrifugal separator called a centrifugal bowl included in the blood component collection circuit is used to separate the blood into components, that is, plasma, a buffy coat, and red blood cells. Platelets are separated from the buffy coat and collected into a container, whereby a platelet product is prepared. The remaining plasma, white blood cells, and red blood cells are returned to the donor.
However, according to the above method, when a large number of platelets is needed, the number of leukocyte (white blood cells) mixed in a platelet product increases. This leads to an increase in the risk of an attack of fever, alloimmunization, virus infection, or the like.
In efforts to cope with the above problem, proposals have been made of a method according to which collected platelets are passed through a leukoreduction filter (leukocyte removal filter) in order to separate or reduce leukocyte, and the platelets separated from the leukocyte are collected in order to prepare a leukocyte reduced platelet product. In this case, platelets remain in the leukoreduction filter. In order to improve the yield of platelets, the leukoreduction filter is cleansed using a cleanser such as physiological saline or an anticoagulant.
However, according to the above method, the cleanser is mixed in the platelet product. This poses a problem that the quality of the platelet product is degraded.